1. Field of the Invention
The present invention relates to a method for automatically adjusting picture frames on a display device.
2. Description of Related Art
As shown in FIG. 1, a computer device 10 comprises a central processing unit 12 (CPU), a display driver 14, a memory 16 and a first communication controller 18. A display device 20 comprises a deflection circuit 22, an imaging circuit 24, a microprocessor 26, a memory 28, a screen 30 and a second communication controller 32. The screen 30 is for displaying picture frames, and the first communication controller 18 and the second communication controller 32 are for exchanging data between the computer device 10 and the display device 20. The display driver 14 outputs synchronous signals to the deflection circuit 22 for determining the horizontal synchronous frequency, the horizontal image timing, the vertical synchronous frequency and the vertical image timing of the displayed picture frame. The display driver 14 also outputs image signals to the imaging circuit 24 for setting the colors of the picture frames to be displayed. The microprocessor 26 can receive the adjusting signals from an on-screen display (OSD) means and change the output signals from the deflection circuit 22 and the imaging circuit 24, so as to adjust the picture frame and the display position of the picture frame to be displayed.
As shown in FIG. 2, the horizontal imaging time corresponding to the displayed picture frame, denoted by C, is set to be covered within the horizontal synchronous time so as to assure normal display of a picture frame. The blanking time is defined to be the sum of the synchronous pulse time (denoted by A), the front entrance time (denoted by B) and the rear entrance time (denoted by D); the blanking time is the flyback time needed for initiating a picture frame. The sum of the synchronous pulse time, the front entrance time, the rear entrance time and the horizontal imaging time defines the horizontal synchronous time, in which the horizontal imaging time is the time required to display a row of picture frames. On the other hand, the vertical imaging time is the time required to display a whole picture frame.
When a user adjusts a picture frame of the display device 20 by OSD means, it is possible that the horizontal imaging time is shifted so that it leads or lags the horizontal synchronous time, and therefore the picture frame cannot be normally displayed. A similar problem may occur in the vertical image timing. So far there is no preferable method to prevent the above-cited problem. There is however a method to adjust the size and position of a picture frame for display entitled “Display” and disclosed by U.S. Pat. No. 5,021,719. The method is disadvantageous in that the sampling of the synchronous time by a microprocessor causes up and down, right and left shifting of a picture frame before the display is optimized, which is time consuming and not appealing to users.
Therefore, it is desirable to provide an improved method for automatically adjusting picture frames on a display device to mitigate and/or obviate the aforementioned problems.